1. Field of the Invention
The present invention relates to a liquid-droplet jetting apparatus which jets (discharges) a droplet of a liquid from a cavity unit by displacing an active portion in a piezoelectric actuator.
2. Description of the Related Art
The liquid-droplet jetting apparatus is exemplified by an ink-jet printer and the like. Japanese Patent Application Laid-open No. 2004-291543, discloses an ink-jet head which applies a jetting pressure from a piezoelectric actuator to a cavity unit provided with a nozzle to thereby jet an ink droplet from the nozzle. In Japanese Patent Application Laid-open No. 2004-291543 (FIGS. 5 and 7), the cavity unit is formed in a substantially flat shape and has a plurality of pressure chambers formed on one surface of the cavity unit and a plurality of nozzles formed on the other surface of the cavity unit; and in the cavity unit, ink-flow channels are formed for the nozzles respectively, each of the ink channels ranging from one of the pressure chambers and reaching up to one of the nozzles.
The piezoelectric actuator has a plurality of piezoelectric layers, a plurality of individual electrodes corresponding to the pressure chambers respectively, and common electrodes. Portions, of each of the piezoelectric layers, each of which is sandwiched between the common and individual electrodes, form active portions which are deformable by a drive voltage applied between the individual and common electrodes. The piezoelectric actuator is stacked on the one surface of the cavity unit in a state that the piezoelectric actuator covers the pressure chambers. In this case, the piezoelectric actuator is arranged on the one surface of the cavity unit so that the active portions correspond to the pressure chambers respectively.
In the ink-jet head constructed in such a manner, the active portions are deformed to thereby change the volume of the pressure chambers in which the ink is filled, so that the ink is jetted from the nozzles corresponding to the pressure chambers respectively. In order that droplet of the ink (ink droplets) are jetted at a predetermined speed, it is necessary to change the volume of the pressure chambers by a predetermined amount.